Governor Greg Abbott, who had lauded the police response to the Texas school shooting, said he was “misled” and is “livid”.
In his earlier statements, Mr Abbott told reporters, he was repeating what he had been told. “The information that I was given turned out, in part, to be inaccurate,” he said on Friday.
Mr Abbott said exactly what happened needs to be “thoroughly, exhaustively” investigated.
The governor previously praised law enforcement for their “amazing courage by running toward gunfire” and their “quick response”.
It comes as Texas Department of Public Safety director Steven McCraw said at a news conference that the on-site commander made the “wrong decision” during the attack.
The commander believed the gunman, 18-year-old Salvador Ramos, was barricaded in a classroom at Robb Elementary School in Uvalde during Tuesday’s attack and that the children were not at risk, he said.
Mr McCraw said: “He was convinced at the time that there was no more threat to the children and that the subject was barricaded and that they had time to organise” to get into the classroom.
On Friday, Mr Abbott had been set to attend the annual convention of the National Rifle Association, which is being held across the state in Houston. Instead he addressed the gun-rights group’s convention by recorded video and went to Uvalde.
At the convention, speaker after speaker took the stage to say that changing US gun laws or further restricting access to firearms is not the answer.
“What stops armed bad guys is armed good guys,” Texas senator Ted Cruz told those gathered in Houston.
Former president Donald Trump was among Republican leaders speaking at the event, where hundreds of protesters angry about gun violence demonstrated outside.
The motive for the massacre remained under investigation. Authorities have said Ramos had no known criminal or mental health history.
During the siege, frustrated onlookers urged police officers to charge into the school, according to witnesses.
“Go in there! Go in there!” women shouted at the officers soon after the attack began, said Juan Carranza, 24, who watched the scene from outside a house across the street.
Javier Cazares, whose fourth grade daughter, Jacklyn Cazares, was killed in the attack, said when he arrived he saw two officers outside the school and about five others escorting students out of the building. But 15 or 20 minutes passed before the arrival of officers with shields, equipped to confront the gunman, he said.
As more parents flocked to the school, he and others pressed police to act, Mr Cazares said. He heard about four gunshots before he and the others were ordered back to a parking lot.
“A lot of us were arguing with the police, ‘You all need to go in there. You all need to do your jobs’. Their response was, ‘We can’t do our jobs because you guys are interfering’,” Mr Cazares said.
The many chilling details of the attack were enough to leave parents struggling with dread.
Visiting a downtown memorial to those killed, Kassandra Johnson of the nearby community of Hondo said she was so worried the day after the attack that she kept her twin boys home from school.
Before she sent the eight-year-olds back, she studied the school building, figuring out which windows she would need to break to reach them. And she drew hearts on their hands with marker, so she could identify them if the worst happened.